A two-phase interim remedial measure plan was developed for the Western Processing Co., Inc. Superfund site with the objective of reducing the quantity of precipitation contacting the site, becoming contaminated, and then running off or infiltrating through the surface. Phase I involved the implementation of a drainage control plan while Phase II, the subject of the paper, involved the installation of an asphalt cap on a portion of the site. Cores were taken from the cap and tested to determine their intrinsic permeability and percent air voids. Intrinsic permeabilities were used to calculate hydraulic conductivities for the cores. The results of the testing showed that the cap was constructed of a relatively permeable asphalt concrete which would not, based on the hydraulic conductivities calculated, result in an impermeable cap. Consequently, achieving the interim remedial measure plan objective had to be based solely on the success of the Phase I drainage control plan.